This was the amazing response when I inquired about Fun Projects VR:
We have all models of our Voltage Regualtors (VR) in stock. We make them for Model T , Model A, V8, and Ford Model N tractors. Original mechanical cutouts have contact points that when worn can stick closed or stick open. When they stick closed the battery is then permanently connected to the generator and attempts to spin it as a motor once the engine ignition is shut off. This will completely discharge the battery if you don't notice that this has happened and have just parked your Model A for the night. Soon after they begin to stick closed and ruin your battery they will stick open. When they stick open the generator is being spun up without any load on it when the engine is running.
Since the field winding is internally wired to the generator output via the 3rd brush, the absence of a load on the generator will allow the generator voltage output to rise which in turns increases the field winding current. This increased field winding current will increase the generator output still higher which will increase the field current still higher yet and the process keeps going with increasing runaway field current and runaway armature current which results in the generator burning its own field winding open or tossing solder out of the armature. This is what has destroyed the vast majority of the early 3rd brush generator as used on the T, A, V8, and N tractors.
When the cutouts go bad the generator and battery get damaged easily. The battery MUST be connected or the generator if spun up will destroy itself. The problem is that the mechanical cutout points simply eventually fail. This is why they are so nasty. Even a good cutout has one issue that hurts the battery and generator and that is that it has no means of sensing the current state of charge of the battery so the cutout based charging system simply charges the battery ANYTIME the engine is running. Whether the battery needs charging or not - it still charges and charges and chartes it.
Our VR looks exactly like a cutout on the outside but although you referred to it as a Voltage Regulator CUTOUT - it is NO such thing. It is a Voltage Regulator. It at all times monitors the battery voltage and regulates the charge which then shuts down the generator once the battery is fully charged. It has no contact points in it so it cannot go open and thus your generator cannot burn up.
Unlike a cutout which simply connects the generator to the battery and charges and charges and charges whenever the engine is running, the VR will only charge up the battery to completely full and then stop charging. This means your generator works a fraction of the time as compared to a cutout. The VR allows you to setup the generator to a high enough charge rate to run the lights at night yet will reduce the charge rate to near zero during the day. This is exactly the function of modern car voltage regulators on generator or alternator equipped modern cars.
Our VR will save your battery and your generator and allow you to drive your Model A with no further adjustment to the generator ever being required once the initial charge rate is set up. There are no modifications required nor recommended to your stock generator.
To date we have sold over 25,000 of them on T, A, V8, and N tractor but also have place our electronics in customer provided "cans" to replace cutouts on non Ford cars like Star, Whippet, Buick, Chevrolet, Dodge...over 100 non Ford regulators are also in the field. Our VR is NOT a cure for a sick electrical system. It needs a good stock generator, good wiring,good battery, and decent ammeter for it all to work right but our VR can be a wonderful addition to a good electrical system. Many of our customers have one on each of their Model A's.